Process for preventing distortion of precious metals at temperatures higher than their fusing-points and article produced thereby



UNITED STATES Pa ENT OFFICE.

RUDOLPH JOHN PESCHKO, OF YORK, PENNSYLVANIA, ASSIGNOR TO SUPPLY COMPANY, A CORPORATION OF'NEW YORK.

THE DENTIST's PROCESS FOR PREVENTING DISTORTION OF PRECIOUS METALS AT TEMPERATURES ,HIG-HER THAN THEIR FUSING-POIN TS AND ARTICLE PRODUCED THEREBY.

No Drawing.

To all whom itmag concern:

Be it known that I, RUDOLPH JOHN PESOHKO, citizen of the United States, and resident of York, county of York, and

State of Pennsylvania, have invented an improvement in processes for preventing distortion of precious metals at temperatures higher than their fusin points and articles produced thereby, of W 10h the following is a specification.

The object of my invention is to provide a method of treating precious metals and their alloys (with or without admixture of basemetalsi, having relatively low fusible temperatures, whereby when subjected to temperatures above their normal fusing point, the said metals or their alloys will retain their shape and may ultimately be cooled without material distortion.

My object is also to provide a construction of article in which precious metals and their alloys (With or without admixtures of base metals). may be attached to refractory bodies in such manner that they be come in eflect cemented directly thereto by a mineral body having affinity for both the refractory body and metal.

My invention consists of the process which comprehends the coating of the precious metals or their alloys aforesaid, with a metal capable of oxidizing at a relatively low temperature so that the precious metal article so coated becomes first metal enameled as it were with the oxid so produced at a temperature less than the fusing temperature of the precious metal or alloy, and thereafter the said skin of oxid sustains the precious metal or alloy against flow under fusion when subjected to temperatures higher than their fusing points.

My invention further consists in the process lastabovedefined when further characterized by uniting the precious metals or their alloys to a refractory body, such as porcelain, for example, by employing for the coating metal one which has direct affinity for the composition of the refractory body as well as aifinity for the precious metalor its alloy.

My invention also consists in an article or product comprising a refractory body to which is attached a precious metal, or alloy thereof, by an interposed metal having, an alloying association wlth the Specification of Letters Patent.

Patented Mar. 30, 1920.

Application filed November 29, 1918 Serial No. 264,528.

with the surface of the precious metal and become oxidized on its exposed portions to become heat resistant and non-fusible, so that the oxid form of the coating acts to sustain the precious metal or its alloy against flow and abnormal distortion when raised to a temperature equal to or somewhat greater than its fusing temperature. It is to be understood that in practising this process it is not essential or necessary that the coating shall be applied to the entire surfaces of the precious metal, as it will suffice in many cases to coat one surface only, such as in a cylinder forexample, in which case the coating need be applied to the outer surface only when thethi'ckness of the walls of the cylinder are thin.

The aluminum oxid will be attached to the surface of the precious metal with great "tenacity owing to the alloying or Welding of a small portion .of the aluminum with the metal of the surface of the precious metal; and where the precious metal is to be attached to a refractory body, the aluminum oxid formed will readily associate with the fused surface of the refractory body, since the composition of such embodies feldspars having strong affinity for the metallic oxids.

While I have obtained satisfactory results from the use of aluminum as the material for coating the precious metal for the purposes of my invention, I do not restrict myself in this respect; and in lieu thereof I may employ other metals such as zinc, magnesium, tin bismuth, antimony and silicon, the alkaline earth metals likev calcium and the rare earth metals, like thorium.

In applying the coating metal, aluminum, etc., I find it convenient to reduce the metal and especially so a to a powdered condition and mix it with an adhesive to form a thick paste and to apply the same to the surface of the precious metal or its alloy. The application of the paste may be accomplished by use of a brush, and it is desirable that too great a thickness shall not be applied where the precious metal article is of a frail or delicate form. The paste may be made of an adhesive composed of an alcoholic solution of a resin such as shellac, the same acting as a carrier for the powdered coatin metal. Any other cement material may e employed, if so desired. The coating should be only sufficient to enable the oxid formed by the heating to'be more or less firmly held to the precious metal surface by the metallic coating metal which attaches itself thereto. The coating metal may be otherwise applied to the surface of the precious metal article, for example, by applying it as a spray, by dipping in a molten bath of the metal, and by electrolytic deposition, and I therefore do not restrict myself to any specific method of applying the coating metal.

While I prefer to employ a simple metal in powdered form mixed with the paste, as the coating material, nevertheless, I do not confine myself thereto, as any combinations of suitable metals fnay be used as mixed powders, or the metals may be fused into an alloy and then powdered, as preferred. Furthermore, the powdered coating metal may be mixed with a salt of a metal, such for example, as mixing the aluminum powder with dry aluminum chlorid or with a zinc salt, so long as the metallic base thereof will become an oxid under the application of heat.

In practice, the precious metal article may be molded into the refractory body or mechanically fitted thereto after the coating material has been applied, and the whole subjected to the necessary heat for insurin the proper reactions, chemical and physica to take place; but in other cases the precious metal article may be subjected to treatment without the presence of the refractory body. While the use .of a coating metal is all that is required, it is possible however to secure satisfactory results by employing a mixture composed wholly or in the main part of an oxid of the metal and incorporating therewith a reducing agent in the form of carbon to sufiiciently reduce the oxid to insure union with the precious metal for supporting the remaining oxid originally present and the oxid formed from the 0x1- dizing of the reduced metals so produced. If the coating metal is in the form of a chlorid or other salt, then a proper reducing admixture should be added to suit the compounds to be thus treated, so that the metal may be in condition to alloy with or adhere to the surface of the precious metal and act as a holder thereto of the oxids to be formed in the coating substances.

I have described my invention in that particularity which I believe is sufficient to a full understanding thereof, and while I have set out what I deem to be the most essential features and results arising therefrom, I do not confine myself to the details of the process or product as the same are susceptible of modifications and Variations without departing from the spirit of the invention.

Having now described my invention what I claim as new and desire to secure by Letters Patent, is:

1. The hereindescribed process for the purpose set out, which consists in coating a precious metal or an alloy thereof with a metal material capable of becoming fused and oxidized at a relatively low temperature, applying heat to the coated metal whereby a portion of the coating metal material becomes fused into the surface of the precious metal and the remaining portion becomes oxidized at a temperature below the fusing point of the precious metal or the alloy thereof and thereby providing an oxid skin to the surface of the precious metal, and employing said oxid skin thereafter to sustain the precious metal or its alloy against flow under fusion when subjected to temperatures higher than their fusing points.

2. The invention defined in claim 1, further characterized by uniting the precious metal or its alloy to a refractory body by fusing the contacting surface of the refractory body to the oxid skin of the coating metal.

3. The process for supporting an article essentially composed of a precious metal material upon a refractory body during the fusing of said body at a temperature higher than that of the melting point of the precious metal material, which consists in interposing between the metal article and surface of the refractory body a metal material having a lower fusing point than that of either the article or body, and gradually applying heat to first fuse the interposed metal material whereby it forms a skin on the article which is securely attached thereto and said skin providing an oxid surface," and finally increasing the temperature to a point higher than the melting point of the metal article and sufficiently to fuse and vitrify the surface of the refractory body to form a cementing union between its earthy constituents and the oxid of the skin.

4. The process specified in claim 1, characterized by employing the' coating metal in the form of a metallic powder made into a paste by admixture with a cementing ma terial by which the metallic powder is cemented to the surface of the precious metal or alloy thereof.

5. The process specified in claim 1 wherein the coating metal is aluminum.

6. The process specified in claim 1, wherein the coating metal is a metallic mixture of aluminum and a low fusing metal salt, capable of oxidizing to form a double oxid at a temperature lower than the fusing temperature of the precious metal or its alloys.

7. An improved article or product comprising a refractory body to which is attached an article of a precious metal or alloy thereof, the attaching means comprising an interposed metal havlng an alloying association with the precious metal or its alloy at a tem erature below the melting point thereof and also having an aflinity for the material of the refractory body when subjected to a temperature equal to or greaterthan the vitrifying point of the refractory body.

8. An improved article for use in connection with a refractory body comprising an article having a coating skin of aluminum thereon, said skin welded to the article and having its exposed portion converted to an oxid said oxid being less fusible than the fusi-bility of the precious metal employed.

In testimony of which invention, I hereunto set my hand.

RUDOLPH JOHN PESCHKO. 

